Billiard Break

Billiard Break Photo Credit: Clipart.com

The early 20th century comedian W.C. Fields used to have an old Vaudeville routine where he'd set up to play a game of pool, and he'd hit all the balls in with one shot. It turns out that the balls had strings attached to them, and an accomplice hiding under the table simply pulled the balls into the pockets. In this Science Update, you'll find out if there's a legitimate way to do what W.C. Fields did, without needing special effects.


A game-ending break. I'm Bob Hirshon and this is Science Update.

Today's Why Is It question concerns the game of pool. Monica Pangilinan of San Diego, California, wants to know if it's physically possible to hit all the balls in on the opening break shot.

Well, Monica, we asked pool player and entertainer Tom Rossman, whose knowledge of "billiardology" has earned him the nickname "Dr. Cue." He says the situation is perhaps possible, but highly improbable.


The most I've ever seen go in on the break, with a rack of 15 balls, has been seven. And in—that's in the game of eight-ball. And in the game of nine-ball, I've seen five go in at one time.

Rossman says differences in humidity tend to give pool tables their own "personality." so even if a player plans the break shot carefully, it's difficult to predict exactly where all the balls will go.


There was a study done many years ago of 10,000 breaks by a conditioned environment in the game of nine-ball. And a ball went in on the break about once every three racks.

So, Rossman says sinking even one ball isn't a sure thing—even for the pros.

If you've racked up some science questions, call us at 1-800-WHY-ISIT. For the American Association for the Advancement of Science, I'm Bob Hirshon.

Making Sense of the Research

The question here is about the science of pool and billiards, but it really opens up to a larger issue: the problem of replicating an event when there are too many variables that can't be controlled.

If there were a way for professional pool players to reliably sink all 15 balls in one shot, at least a handful of them would have learned to do it by now. Even if all the physical conditions of the balls and the table were exactly the same, that would be very tricky, because the player would have to execute an exact set of muscular movements to produce a strike with exactly the right amount of force on exactly the right spot on the cue ball. Even for a pro, that's a tall order.

But as Rossman explains, it's made worse by all the subtle differences in physical conditions that a player has no way of even measuring, much less controlling. For example, moisture from the air can collect on the surface of the balls, and affect their speed and the way they interact with each other. (That's because the moisture changes the amount of friction between the ball, the table, and the other balls). Also, the tables themselves vary in surface properties, and that can affect the way the balls move. And any slight flaws in the surface of either the table or the balls can make a difference too, even if they're not noticeable to the naked eye.

The problem of too many variables isn't restricted to billiards. Any time you're trying to achieve a very precise outcome in a complicated process that takes place outside a laboratory, you're going to run up against all kinds of invisible, hard-to-control factors. That's why even pro bowlers rarely score a perfect 300, and why top major league hitters only get a hit once every three times at bat.

It's also why a genetic clone of Michael Jordan wouldn't necessarily be a great basketball player: there are all kinds of other influences on the real Michael Jordan's life, biological and environmental, that made him a great athlete besides just his genes. And trying to reproduce all those variables in another person's life would be impossible, even if that person were genetically identical.

On the plus side, all these variables make life more interesting. Pool would be pretty boring if a good player could sink all 15 balls on the first shot, and basketball would be pretty boring if we could raise entire teams of genetically engineered Michael Jordan clones.

Now try and answer these questions:

  1. Other than the player's ability, what are some factors that influence how many pool balls will sink after a break?
  2. To what extent can a player control these factors?
  3. Think of some other sports or games. What factors might affect the performance of a player besides his or her own physical abilities?
  4. Can you think of other situations in which different outcomes are produced by roughly the same action? What factors are in play there?

For Educators

Paper Pool allows students to explore the mathematics and physics of pool through classroom lessons and an interactive applet.

Sport! Science is the Exploratorium's website devoted to the science of various sports.

Chaos is a lesson plan that allows students to explore various incarnations of chaos (small changes in variables leading to large changes in outcome).

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